This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the
W3C.

This document is the first public working draft of this specification. It should in no way be considered stable, and should not be referenced for any purposes whatsoever. This version does
not include the implementations of XHTML 2.0 in either DTD or XML Schema form. Those will be included in subsequent versions, once the contents of this language stabilizes.

At the time of publication, the Working Group believed there were zero patent disclosures relevant to this specification. A current list of patent disclosures relevant to this specification may be
found on the Working Group's patent disclosure page.

XHTML 2 is a markup language intended for rich, portable web-based applications. While the ancestry of XHTML 2 comes from HTML 4, XHTML 1.0, and XHTML 1.1, it is not intended to be
backward compatible with its earlier versions. Application developers familiar with earlier its ancestors will be comfortable working with XHTML 2. Appendix A
describes the ways in which XHTML 2 differs from previous versions and what application developers need to know to convert existing applications to XHTML 2.

XHTML 2 is a member of the XHTML Family of markup languages. It is an XHTML Host Language as defined in XHTML Modularization. As such, it is made up of a set of XHTML Modules that together
describe the elements and attributes of the language, and their content model. XHTML 2 updates many of the modules defined in XHTML Modularization 1.0 [XHTMLMOD], and includes the updated versions of all those modules and their semantics. XHTML 2 also uses modules from Ruby [RUBY], XML Events [XMLEVENTS], and XForms [XFORMS].

The modules defined in this specification are largely extensions of the modules defined in XHTML Modularization 1.0. This specification also defines the semantics of the modules it includes. So,
that means that unlike earlier versions of XHTML that relied upon the semantics defined in HTML 4, all of the semantics for XHTML 2 are defined either in this specification or in the specifications
that it normatively references.

Even though the XHTML 2 modules are defined in this specification, they are available for use in other XHTML family markup languages. Over time, it is possible that the modules defined in this
specification will migrate into the XHTML Modularization specification.

While some terms are defined in place, the following definitions are used throughout this document. Familiarity with the W3C XML 1.0 Recommendation [XML] is highly recommended.

abstract module

a unit of document type specification corresponding to a distinct type of content, corresponding to a markup construct reflecting this distinct type.

content model

the declared markup structure allowed within instances of an element type. XML 1.0 differentiates two types: elements containing only element content (no character data) and mixed content
(elements that may contain character data optionally interspersed with child elements). The latter are characterized by a content specification beginning with the "#PCDATA" string (denoting character
data).

a feature marked as deprecated is in the process of being removed from this recommendation. Portable applications should not use features marked as deprecated.

document model

the effective structure and constraints of a given document type. The document model constitutes the abstract representation of the physical or semantic structures of a class of documents.

document type

a class of documents sharing a common abstract structure. The ISO 8879 [SGML] definition is as follows: "a class of documents having similar
characteristics; for example, journal, article, technical manual, or memo. (4.102)"

document type definition (DTD)

a formal, machine-readable expression of the XML structure and syntax rules to which a document instance of a specific document type must conform; the schema type used in XML 1.0 to validate
conformance of a document instance to its declared document type. The same markup model may be expressed by a variety of DTDs.

driver

a generally short file used to declare and instantiate the modules of a DTD. A good rule of thumb is that a DTD driver contains no markup declarations that comprise any part of the document model
itself.

element

an instance of an element type.

element type

the definition of an element, that is, a container for a distinct semantic class of document content.

entity

an entity is a logical or physical storage unit containing document content. Entities may be composed of parse-able XML markup or character data, or unparsed (i.e., non-XML, possibly non-textual)
content. Entity content may be either defined entirely within the document entity ("internal entities") or external to the document entity ("external entities"). In parsed entities, the replacement
text may include references to other entities.

the name identifying the element type of an element. Also, element type name.

hybrid document

A hybrid document is a document that uses more than one XML namespace. Hybrid documents may be defined as documents that contain elements or attributes from hybrid document types.

instantiate

to replace an entity reference with an instance of its declared content.

markup declaration

a syntactical construct within a DTD declaring an entity or defining a markup structure. Within XML DTDs, there are four specific types: entity declaration defines the binding between a mnemonic
symbol and its replacement content; element declaration constrains which element types may occur as descendants within an element (see also content model); attribute definition list declaration
defines the set of attributes for a given element type, and may also establish type constraints and default values; notation declaration defines the binding between a notation name and an external
identifier referencing the format of an unparsed entity.

markup model

the markup vocabulary (i.e., the gamut of element and attribute names, notations, etc.) and grammar (i.e., the prescribed use of that vocabulary) as defined by a document type definition (i.e., a
schema) The markup model is the concrete representation in markup syntax of the document model, and may be defined with varying levels of strict conformity. The same document model may be expressed
by a variety of markup models.

module

an abstract unit within a document model expressed as a DTD fragment, used to consolidate markup declarations to increase the flexibility, modifiability, reuse and understanding of specific
logical or semantic structures.

modularization

an implementation of a modularization model; the process of composing or de-composing a DTD by dividing its markup declarations into units or groups to support specific goals. Modules may or may
not exist as separate file entities (i.e., the physical and logical structures of a DTD may mirror each other, but there is no such requirement).

modularization model

the abstract design of the document type definition (DTD) in support of the modularization goals, such as reuse, extensibility, expressiveness, ease of documentation, code size, consistency and
intuitiveness of use. It is important to note that a modularization model is only orthogonally related to the document model it describes, so that two very different modularization models may
describe the same document type.

parameter entity

an entity whose scope of use is within the document prolog (i.e., the external subset/DTD or internal subset). Parameter entities are disallowed within the document instance.

parent document type

A parent document type of a hybrid document is the document type of the root element.

tag

descriptive markup delimiting the start and end (including its generic identifier and any attributes) of an element.

The root element of the document must contain an xmlns declaration for the XHTML 2.0 namespace [XMLNAMES]. The namespace for
XHTML is defined to be http://www.w3.org/2002/06/xhtml2. An example root element might look like:

<html xmlns="http://www.w3.org/2002/06/xhtml2" xml:lang="en">

There must be a DOCTYPE declaration in the document prior to the root element. If present, the public identifier included in the DOCTYPE declaration must reference the DTD found in Appendix C using its Formal Public Identifier. The system identifier may be modified appropriately.

Note that in this example, the XML declaration is included. An XML declaration like the one above is not required in all XML documents. XHTML document authors are strongly encouraged to use XML
declarations in all their documents. Such a declaration is required when the character encoding of the document is other than the default UTF-8 or UTF-16 and no encoding was determined by a
higher-level protocol.

The XHTML 2.0 document type is a fully functional document type with rich semantics. It is a collection of XHTML-conforming modules (most of which are defined in this specification). The Modules
and their elements are listed here for information purposes, but the definitions in their base documents should be considered authoritative. In the on-line version of this document, the module names
in the list below link into the definitions of the modules within the relevant version of the authoritative specification.

Need XHTML 2.0 Definition Table

We need a table that defines the modules that are in XHTML 2.0 and links them into this document. Currently, that will be a bunch of modules that are in this document, and modules from XML Events,
Ruby, and XForms. The table below is largely correct, but is still just a place holder.

A detailed description of the behavior of the element, if appropriate.

Note that attributes are fully defined only the first time they are used in each module. After that, only a brief description of the attribute is provided, along with a link back
to the primary definition.

An abstract module is a definition of an XHTML module using prose text and some informal markup conventions. While such a definition is not generally useful in the machine processing of document
types, it is critical in helping people understand what is contained in a module. This section defines the way in which XHTML abstract modules are defined. An XHTML-conforming module is not
required to provide an abstract module definition. However, anyone developing an XHTML module is encouraged to provide an abstraction to ease in the use of that module.

The abstract modules are not defined in a formal grammar. However, the definitions do adhere to the following syntactic conventions. These conventions are similar to those of XML DTDs, and should
be familiar to XML DTD authors. Each discrete syntactic element can be combined with others to make more complex expressions that conform to the algebra defined here.

element name

When an element is included in a content model, its explicit name will be listed.

content set

Some modules define lists of explicit element names called content sets. When a content set is included in a content model, its name will be listed.

expr ?

Zero or one instances of expr are permitted.

expr +

One or more instances of expr are required.

expr *

Zero or more instances of expr are permitted.

a , b

Expression a is required, followed by expression b.

a | b

Either expression a or expression b is required.

a - b

Expression a is permitted, omitting elements in expression b.

parentheses

When an expression is contained within parentheses, evaluation of any subexpressions within the parentheses take place before evaluation of expressions outside of the parentheses (starting at the
deepest level of nesting first).

extending pre-defined elements

In some instances, a module adds attributes to an element. In these instances, the element name is followed by an ampersand (&).

defining required attributes

When an element requires the definition of an attribute, that attribute name is followed by an asterisk (*).

defining the type of attribute values

When a module defines the type of an attribute value, it does so by listing the type in parentheses after the attribute name.

defining the legal values of attributes

When a module defines the legal values for an attribute, it does so by listing the explicit legal values (enclosed in quotation marks), separated by vertical bars (|), inside of
parentheses following the attribute name. If the attribute has a default value, that value is followed by an asterisk (*). If the attribute has a fixed value, the attribute name is
followed by an equals sign (=) and the fixed value enclosed in quotation marks.

Abstract module definitions define minimal, atomic content models for each module. These minimal content models reference the elements in the module itself. They may also reference elements in
other modules upon which the abstract module depends. Finally, the content model in many cases requires that text be permitted as content to one or more elements. In these cases, the symbol used for
text is PCDATA. This is a term, defined in the XML 1.0 Recommendation, that refers to processed character data. A content type can also be defined as EMPTY, meaning the element has no content in its minimal content model.

In some instances, it is necessary to define the types of attribute values or the explicit set of permitted values for attributes. The following attribute types (defined in the XML 1.0
Recommendation) are used in the definitions of the abstract modules:

Used by the class attribute, ClassNames are tokens that identify an element as being a member of the set
named by the value of the class attribute. ClassName attribute tokens must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores
("_"), colons (":"), and periods (".").

Authors may use the following recognized link types, listed here with their conventional interpretations. A LinkTypes value refers to a space-separated list of link types. White space characters
are not permitted within link types.

These link types are case-insensitive, i.e., "Alternate" has the same meaning as "alternate".

User agents, search engines, etc. may interpret these link types in a variety of ways. For example, user agents may provide access to linked documents through a navigation bar.

Alternate

Designates substitute versions for the document in which the link occurs. When used together with the hreflang attribute, it implies a translated version of the document. When used
together with the media attribute, it implies a version designed for a different medium (or media).

Stylesheet

Refers to an external style sheet. See the Style Sheet Module for details. This is used together with the link type "Alternate" for
user-selectable alternate style sheets.

Start

Refers to the first document in a collection of documents. This link type tells search engines which document is considered by the author to be the starting point of the collection.

Next

Refers to the next document in a linear sequence of documents. User agents may choose to pre-load the "next" document, to reduce the perceived load time.

Prev

Refers to the previous document in an ordered series of documents. Some user agents also support the synonym "Previous".

Contents

Refers to a document serving as a table of contents. Some user agents also support the synonym ToC (from "Table of Contents").

Index

Refers to a document providing an index for the current document.

Glossary

Refers to a document providing a glossary of terms that pertain to the current document.

Copyright

Refers to a copyright statement for the current document.

Chapter

Refers to a document serving as a chapter in a collection of documents.

Section

Refers to a document serving as a section in a collection of documents.

Subsection

Refers to a document serving as a subsection in a collection of documents.

Appendix

Refers to a document serving as an appendix in a collection of documents.

Help

Refers to a document offering help (more information, links to other sources information, etc.)

Bookmark

Refers to a bookmark. A bookmark is a link to a key entry point within an extended document. The title attribute may be used, for example, to label the bookmark.
Note that several bookmarks may be defined in each document.

The value may be a Length or a relative length. A relative length has the form "i*", where "i" is an integer. When allotting space among elements competing for that space, user agents allot pixel
and percentage lengths first, then divide up remaining available space among relative lengths. Each relative length receives a portion of the available space that is proportional to the integer
preceding the "*". The value "*" is equivalent to "1*". Thus, if 60 pixels of space are available after the user agent allots pixel and percentage space, and the competing relative lengths are 1*,
2*, and 3*, the 1* will be allotted 10 pixels, the 2* will be allotted 20 pixels, and the 3* will be allotted 30 pixels.

The value is an integer that represents the number of pixels of the canvas (screen, paper). Thus, the value "50" means fifty pixels. For normative information about the definition of a pixel,
please consult [CSS2]

Many of the abstract modules in this document define the required attributes for their elements. The table below defines some collections of attributes that are referenced throughout the modules.
These expressions should in no way be considered normative or mandatory. They are an editorial convenience for this document. When used in the remainder of this section, it is the expansion of the
term that is normative, not the term itself.

The following basic attribute sets are used on many elements. In each case where they are used, their use is identified via their collection name.

This attribute assigns one or more class names to an element; the element may be said to belong to these classes. A class name may be shared by several element instances.

The class attribute can be used for different purposes in XHTML, for instance as a style sheet selector (when an author wishes to assign style information to a set of elements), and for general purpose processing by user agents.

For instance in the following example, the p element is used in conjunction with the class attribute to identify a particular type of paragraph.

<p><span class="note">
These programs are only available if you have purchased the advanced professional suite.
</p>

Style sheets rules can then be used to render the paragraph appropriately, for instance by putting a border round it, giving it a different background colour, or where necessary by not displaying
it at all.

This attribute offers advisory information about the element for which it is set.

Values of the title attribute may be rendered by user agents in a variety of ways. For instance, visual
browsers should display the title as a "tool tip" (a short message that appears when the pointing device pauses over an object). Audio user agents may speak the title information in a similar
context.

This attribute specifies the base language of an element's attribute values and text content. It is defined normatively in [XML] section 2.12 http://www.w3.org/TR/REC-xml#sec-lang-tag. The
default value of this attribute is unspecified.

An element inherits language code information according to the following order of precedence (highest to lowest):

The closest parent element that has the xml:lang attribute set (i.e., the xml:lang attribute is inherited).

The HTTP "Content-Language" header (which may be configured in a server).

In this example, the primary language of the document is French ("fr"). One paragraph is declared to be in US English ("en-us"), after which the primary language returns to French. The following
paragraph includes an embedded Japanese ("ja") phrase, after which the primary language returns to French.

This attribute assigns an access key to an element. An access key is a single character from the document character set.
Note. Authors should consider the input method of the expected reader when specifying an accesskey.

Pressing an access key assigned to an element gives focus to the element. The action that occurs when an element receives focus
depends on the element. For example, when a user activates a link defined by the a element, the user agent generally follows the link.
When a user activates a radio button, the user agent changes the value of the radio button. When the user activates a text field, it allows input, etc.

In this example, we assign an access key to a link defined by the a element. Typing this access key takes the user to another
document, in this case, a table of contents.

The invocation of access keys depends on the underlying system. For instance, on machines running MS Windows, one generally has to press the "alt" key in addition to the access key. On Apple
systems, one generally has to press the "cmd" key in addition to the access key.

The rendering of access keys depends on the user agent. We recommend that authors include the access key in label text or wherever the access key is to apply. User agents should render the value
of an access key in such a way as to emphasize its role and to distinguish it from other characters (e.g., by underlining it).

This attribute specifies the position of the current element in the navingation order for the current document. This value must be a number between 0 and 32767. User agents must ignore leading
zeros.

The navigation order defines the order in which elements will receive focus when navigated by the user via the keyboard. The
navigation order may include elements nested within other elements.

Elements that may receive focus should be navigated by user agents according to the following rules:

Those elements that support the navindex attribute and assign a positive value to it are navigated
first. Navigation proceeds from the element with the lowest navindex value to the element with the
highest value. Values need not be sequential nor must they begin with any particular value. Elements that have identical navindex values should be navigated in the order they appear in the character stream.

Those elements that do not support the navindex attribute or support it and assign it a value of "0"
are navigated next. These elements are navigated in the order they appear in the character stream.

Elements that are disabled do not participate in the navigation order.

Tabbing keys. The actual key sequence that causes navigation or element activation depends on the configuration of the user agent (e.g., the "tab" key is used for navigation
and the "enter" key is used to activate a selected element).

User agents may also define key sequences to navigate the navigation order in reverse. When the end (or beginning) of the navigation order is reached, user agents may circle back to the
beginning (or end).

The global attributes from [XMLEVENTS] are included in the Events attribute collection. The normative definition of those attributes and
their semantics is included in that specification. They are described briefly below:

This attribute specifies whether an event should stop propagating after this observer processes it, or continue down the event chain for possible further processing. If not specified, the default
value of this attribute is continue.

This attribute specifies the id of the target element of the event (i.e., the node that caused the event). If not specified, the default value of this attribute is the element on which the event
attribute is specified.

Note that these attributes are not in the XHTML namespace. Instead, they are in the XML Events namespace. The XHTML namespace is the default namespace for XHTML documents, so
XHTML elements and attributes do not require namespace prefixes (although they are permitted). XML Events attributes MUST use a prefix, since they are not in the default namespace of the document.
When XML Events are included in an XHTML document, the default prefix for those attribute is ev.

The Structure Module defines the major structural elements for XHTML. These elements effectively act as the basis for the content model of many XHTML family document types. The elements and
attributes included in this module are:

This module is the basic structural definition for XHTML content. The html element acts as the root element for all XHTML Family Document Types.

Note that the value of the xmlns attribute is defined to be "http://www.w3.org/2002/06/xhtml2". Also note that because the xmlns attribute is treated specially by XML namespace-aware parsers [XMLNAMES], it is legal to have it present as an attribute of each element. However, any time the xmlns attribute is used in the context of an
XHTML module, whether with a prefix or not, the value of the attribute shall be the XHTML namespace defined here.

This attribute specifies the location of one or more meta data profiles, separated by white space. For future extensions, user agents should consider the value to be a list even though this
specification only considers the first URI to be significant. Profiles are discussed in the section on meta data.

The head element contains information about the current document, such as its title, keywords that may be useful to search
engines, and other data that is not considered document content. User agents do not generally render elements that appear in the head
as content. They may, however, make information in the head available to users through other mechanisms.

Authors should use the title element to identify the contents of a document.
Since users often consult documents out of context, authors should provide context-rich titles. Thus, instead of a title such as "Introduction", which doesn't provide much contextual background,
authors should supply a title such as "Introduction to Medieval Bee-Keeping" instead.

For reasons of accessibility, user agents must always make the content of the title element available to users (including title elements that occur in frames). The mechanism for doing so
depends on the user agent (e.g., as a caption, spoken).

Titles may contain entity references (for accented characters, special characters, etc.), but may not contain other markup (including comments).
Here is a sample document title:

The body of a document contains the document's content. The content may be presented by a user agent in a variety of ways. For example, for visual browsers, you can think of the body as a canvas
where the content appears: text, images, colors, graphics, etc. For audio user agents, the same content may be spoken.

Note that the use of the words Block and Inline here are meant to be suggestive of the role the content sets play. They are not normative with regards to presentation (in other
words, a style sheet might give an element within the Block content a display property of inline).

The content of the abbr and acronym elements specifies the abbreviated expression
itself, as it would normally appear in running text. The title attribute of these elements may be used to
provide the full or expanded form of the expression.

Note that abbreviations and acronyms often have idiosyncratic pronunciations. For example, while "IRS" and "BBC" are typically pronounced letter by letter, "NATO" and "UNESCO" are pronounced
phonetically. Still other abbreviated forms (e.g., "URI" and "SQL") are spelled out by some people and pronounced as words by other people. When necessary, authors should use style sheets to specify
the pronunciation of an abbreviated form.

The acronym element indicates that a text fragment is an acronym (e.g., BBC, WWW, URL, etc.). Its usage is the same as the abbr element above.

While some dictionaries define an acronym to be just a word formed from the initial letters of other words, others require the acronym to be pronouncable as a word. This specification does not
require the acronym element to adhere to either definition, but is only provided for author convenience.

The value of this attribute is a URI that designates a source document or message. This attribute is intended to give further information about the element's contents (e.g., the source from which
a quotation was borrowed, or the reason text was inserted or deleted). User Agents should provide a means for the user to access the further information.

This example formats an excerpt from "The Two Towers", by J.R.R. Tolkien, as a blockquote.

<blockquote cite="http://www.example.com/tolkien/twotowers.html">
<p>They went in single file, running like hounds on a strong scent,
and an eager light was in their eyes. Nearly due west the broad
swath of the marching Orcs tramped its ugly slot; the sweet grass
of Rohan had been bruised and blackened as they passed.</p>
</blockquote>

The value of this attribute is a URI that designates a source document or message. This attribute is intended to give further information about the element's contents (e.g., the source from which
a quotation was borrowed, or the reason text was inserted or deleted). User Agents should provide a means for the user to access the further information.

In the following example, the cite element is used to delineate the speaker:

As <cite cite="http://www.whitehouse.gov/history/presidents/ht33.html">Harry S. Truman</cite> said,
<quote lang="en-us">The buck stops here.</quote>
More information can be found in <cite cite="http://www.w3.org/TR/REC-xml">[XML]</cite>.

The div element, in conjunction with the id and class attributes, offer a generic mechanism for adding structure to documents. This element defines no
presentational idioms on the content. Thus, authors may use this element in conjunction with style sheets, the xml:lang attribute, etc., to tailor XHTML to their own needs and tastes.

There are two styles of headings in XHTML: the numbered versions h1, h2 etc.,
and the structured version h, which is used in combination with the section
element.

There are six levels of numbered headings in XHTML with h1 as the most important and h6 as the least. The visual presentation of headers can render more important headings in larger fonts than less important ones.

Structured headings use the single h element, in combination with the section element to indicate
the structure of the document, and the nesting of the sections indicate the importance of the heading.

Numbered sections and references
XHTML does not itself cause section numbers to be generated from headings. Style sheet
languages such as CSS however allow authors to control the generation of section numbers.

The practice of skipping heading levels is considered to be bad practice. The series h1 h2
h1 is acceptable, while h1 h3 h1 is not, since the heading level h2 has been skipped.

The line element represents a sub-paragraph. It is intended as a structured replacement for the br element. It contains a piece of text that when visually represented should start on a new line, and have a line break at the end. Whether the line should wrap or
not visually depends on styling properties of the element.

By retaining structure in text that has to be broken over lines, you retain essential information about its makeup. This gives you greater freedom with styling the content. For instance, line
numbers can be generated automatically from the stylesheet if needed.

In comparison with earlier versions of HTML, where a paragraph could only contain inline text, XHTML2's paragraphs represent the conceptual idea of a paragraph, and so may contain lists,
blockquotes, pre's and tables as well as inline text. They may not, however, contain directly nested p elements.

The pre element indicates that whitespace in the enclosed text has semantic relevance, and will normally be included in renderings of the
content

Note that all elements in the XHTML family preserve their whitespace in the document, which is only removed on rendering, via a stylesheet, according to the rules of CSS [CSS]. This means that in
principle all elements may preserve or collapse whitespace on rendering, under control of a stylesheet. Also note that there is no requirement that the <pre> element be rendered in a
monospace font (although this is the default rendering), nor that text wrapping be disabled.

The value of this attribute is a URI that designates a source document or message. This attribute is intended to give further information about the element's contents (e.g., the source from which
a quotation was borrowed, or the reason text was inserted or deleted). User Agents should provide a means for the user to access the further information.

Visual user agents are not required to add delimiting quotation marks (as was the case for the q element in earlier versions of HTML). It is the responsibility of the document author
to add any required quotation marks.

The following example illustrates nested quotations with the quote element.

<p>John said, <quote lang="en-us">"I saw Lucy at lunch, she told me
<quote lang="en-us">'Mary wants you
to get some ice cream on your way home.'</quote> I think I will get
some at Jen and Berry's, on Gloucester Road."</quote></p>

The section element, in conjunction with the h element, offers a mechanism for
structuring documents into sections. This element defines content to be block-level but imposes no other presentational idioms on the content, which may otherwise be controlled from a style
sheet.

By representing the structure of documents explicitely using the section and h
elements gives the author greater control over presentation possibilities than the traditional implicit structuring using numbered levels of headings. For instance, it is then possible to indicate
the nesting of sections by causing a border to be displayed to the left of sections.

The span element, in conjunction with the id and class attributes, offer a generic mechanism for adding structure to documents. This element imposes no
presentational idioms on the content. Thus, authors may use this element in conjunction with style sheets, the xml:lang attribute, etc., to tailor XHTML to their own needs and tastes.

This attribute gives an advisory hint as to the content type of the content available at the link target address. It allows user agents to opt to use a fallback mechanism rather than fetch the
content if they are advised that they will get content in a content type they do not support.

Authors who use this attribute take responsibility to manage the risk that it may become inconsistent with the content available at the link target address.

For the current list of registered content types, please consult [MIMETYPES].

This attribute specifies the position of the current element in the navingation order for the current document. This value must be a number between 0 and 32767. User agents must ignore leading
zeros.

The navigation order defines the order in which elements will receive focus when navigated by the user via the keyboard. The navigation order may
include elements nested within other elements.

Elements that may receive focus should be navigated by user agents according to the following rules:

Those elements that support the navindex attribute and assign a positive value to it are navigated first. Navigation proceeds
from the element with the lowest navindex value to the element with the highest value. Values need not be sequential nor must
they begin with any particular value. Elements that have identical navindex values should be navigated in the order they appear
in the character stream.

Those elements that do not support the navindex attribute or support it and assign it a value of "0" are navigated next.
These elements are navigated in the order they appear in the character stream.

Elements that are disabled do not participate in the navigation order.

Tabbing keys. The actual key sequence that causes navigation or element activation depends on the configuration of the user agent (e.g., the "tab" key is used for navigation
and the "enter" key is used to activate a selected element).

User agents may also define key sequences to navigate the navigation order in reverse. When the end (or beginning) of the navigation order is reached, user agents may circle back to the
beginning (or end).

The href attribute makes this anchor the source anchor of exactly one link.

Authors may also create an a element that specifies no anchors, i.e., that doesn't specify href, or id. Values for these attributes
may be set at a later time through scripts as defined in the Scripting module.

In the example that follows, the a element defines a link. The source anchor is the text "W3C Web site" and the destination anchor is
"http://www.w3.org/":

For more information about W3C, please consult the
<a href="http://www.w3.org/">W3C Web site</a>.

This link designates the home page of the World Wide Web Consortium. When a user activates this link in a user agent, the user agent will retrieve the resource, in this case, an XHTML
document.

User agents generally render links in such a way as to make them obvious to users (underlining, reverse video, etc.). The exact rendering depends
on the user agent. Rendering may vary according to whether the user has already visited the link or not. A possible visual rendering of the previous link might be:

For more information about W3C, please consult the W3C Web site.
~~~~~~~~~~~~

To tell user agents explicitly what the character encoding of the destination page is, set the charset attribute:

For more information about W3C, please consult the
<a href="http://www.w3.org/" charset="ISO-8859-1">W3C Web site</a>

Suppose we define an anchor named "anchor-one" in the file "one.html".

...text before the anchor...
<a name="anchor-one">This is the location of anchor one.</a>
...text after the anchor...

This creates an anchor around the text "This is the location of anchor one.". Usually, the contents of a are not rendered in any
special way when a defines an anchor only.

Having defined the anchor, we may link to it from the same or another document. URIs that designate anchors contain a "#" character followed by the anchor name (the fragment identifier). Here are
some examples of such URIs:

An absolute URI: http://www.mycompany.com/one.html#anchor-one

A relative URI: ./one.html#anchor-one or one.html#anchor-one

When the link is defined in the same document: #anchor-one

Thus, a link defined in the file "two.html" in the same directory as "one.html" would refer to the anchor as follows:

...text before the link...
For more information, please consult <a href="./one.html#anchor-one"> anchor one</a>.
...text after the link...

The a element in the following example specifies a link (with href) and creates a named anchor (with id)
simultaneously:

I just returned from vacation! Here's a
<a id="anchor-two"
href="http://www.somecompany.com/People/Ian/vacation/family.png">
photo of my family at the lake.</a>.

This example contains a link to a different type of Web resource (a PNG image). Activating the link should cause the image resource to be retrieved from the Web (and possibly displayed if the
system has been configured to do so).

Note. User agents area required to find anchors created by empty a elements.

An ordered list, created using the ol element, should contain information where order should be emphasized, as in a recipe:

Mix dry ingredients thoroughly.

Pour in wet ingredients.

Mix for 10 minutes.

Bake for one hour at 300 degrees.

Definition lists, created using the dl element, generally consist of a series of term/definition pairs (although definition lists may have
other applications). Thus, when advertising a product, one might use a definition list:

Lower cost

The new version of this product costs significantly less than the previous one!

Easier to use

We've changed the product so that it's much easier to use!

Safe for kids

You can leave your kids alone in a room with this product and they won't get hurt (not a guarantee).

defined in XHTML as:

<dl>
<dt><strong>Lower cost</strong></dt>
<dd>The new version of this product costs significantly less than the
previous one!</dd>
<dt><strong>Easier to use</strong></dt>
<dd>We've changed the product so that it's much easier to
use!</dd>
<dt><strong>Safe for kids</strong></dt>
<dd>You can leave your kids alone in a room with this product and
they won't get hurt (not a guarantee).</dd>
</dl>

Lists may also be nested and different list types may be used together, as in the following example, which is a definition list that contains an unordered list (the ingredients) and an ordered
list (the procedure):

The ingredients:

100 g. flour

10 g. sugar

1 cup water

2 eggs

salt, pepper

The procedure:

Mix dry ingredients thoroughly.

Pour in wet ingredients.

Mix for 10 minutes.

Bake for one hour at 300 degrees.

Notes:

The recipe may be improved by adding raisins.

The exact presentation of the three list types depends on the user agent. We discourage authors from using lists purely as a means of indenting text. This is a stylistic issue and is properly
handled by style sheets.

Definition lists vary only slightly from other types of lists in that list items consist of two parts: a term and a description. The term is given by the dt element and is restricted to inline content. The description is given with a dd element that contains
block-level content.

<dl>
<dt>Center</dt>
<dt>Centre</dt>
<dd> A point equidistant from all points
on the surface of a sphere.</dd>
<dd> In some field sports, the player who
holds the middle position on the field, court,
or forward line.</dd>
</dl>

Another application of dl, for example, is for marking up dialogues, with each dt naming
a speaker, and each dd containing his or her words.

Navigation lists are intended to be used to define collections of selectable items for presentation in a "navigation" menu. A navigation list is required to start with a name element that defines the name for the list.

On visual user agents, the default presentation behavior is as follows:

Ordered and unordered lists are rendered in an identical manner except that visual user agents number ordered list items. User agents may present those numbers in a variety of ways. Unordered list
items are not numbered.

Both types of lists are made up of sequences of list items defined by the li element.

This attribute assigns an access key to an element. An access key is a single character from the document character set. Note.
Authors should consider the input method of the expected reader when specifying an accesskey.

Pressing an access key assigned to an element gives focus to the element. The action that occurs when an element receives focus depends on the
element. For example, when a user activates a link defined by the a element, the user agent generally follows the link. When a user
activates a radio button, the user agent changes the value of the radio button. When the user activates a text field, it allows input, etc.

In this example, we assign an access key to a link defined by the a element. Typing this access key takes the user to another
document, in this case, a table of contents.

The invocation of access keys depends on the underlying system. For instance, on machines running MS Windows, one generally has to press the "alt" key in addition to the access key. On Apple
systems, one generally has to press the "cmd" key in addition to the access key.

The rendering of access keys depends on the user agent. We recommend that authors include the access key in label text or wherever the access key is to apply. User agents should render the value
of an access key in such a way as to emphasize its role and to distinguish it from other characters (e.g., by underlining it).

This attribute specifies the position of the current element in the navingation order for the current document. This value must be a number between 0 and 32767. User agents must ignore leading
zeros.

The navigation order defines the order in which elements will receive focus when navigated by the user via the keyboard. The navigation order may
include elements nested within other elements.

Elements that may receive focus should be navigated by user agents according to the following rules:

Those elements that support the navindex attribute and assign a positive value to it are navigated first. Navigation proceeds from the
element with the lowest navindex value to the element with the highest value. Values need not be sequential nor must they begin with any
particular value. Elements that have identical navindex values should be navigated in the order they appear in the character stream.

Those elements that do not support the navindex attribute or support it and assign it a value of "0" are navigated next. These elements
are navigated in the order they appear in the character stream.

Elements that are disabled do not participate in the navigation order.

Tabbing keys. The actual key sequence that causes navigation or element activation depends on the configuration of the user agent (e.g., the "tab" key is used for navigation
and the "enter" key is used to activate a selected element).

User agents may also define key sequences to navigate the navigation order in reverse. When the end (or beginning) of the navigation order is reached, user agents may circle back to the
beginning (or end).

The li element defines a list item within an ordered, unordered, or navigation list. When the href attribute is defined, the contents of the list item become a selectable link, just as an a element with an href attribute would be.

The bidirectional algorithm and the dir attribute generally suffice to manage embedded direction changes. However, some situations may arise
when the bidirectional algorithm results in incorrect presentation. The bdo element allows authors to
turn off the bidirectional algorithm for selected fragments of text.

This mandatory attribute specifies the base direction of the element's text content. This direction overrides the inherent directionality of characters as defined in [UNICODE]. Possible values:

ltr: Left-to-right text.

rtl: Right-to-left text.

Consider a document containing the same text as before:

english1 HEBREW2 english3 HEBREW4 english5 HEBREW6

but assume that this text has already been put in visual order. One reason for this may be that the MIME standard ([RFC2045], [RFC1556]) favors visual order, i.e., that right-to-left character sequences are inserted right-to-left in the byte stream. In an email, the above might
be formatted, including line breaks, as:

english1 2WERBEH english3
4WERBEH english5 6WERBEH

This conflicts with the [UNICODE] bidirectional algorithm, because that algorithm would invert 2WERBEH, 4WERBEH, and
6WERBEH a second time, displaying the Hebrew words left-to-right instead of right-to-left.

The solution in this case is to override the bidirectional algorithm by putting the Email excerpt in a pre element (to conserve line breaks)
and each line in a bdo element, whose dir attribute is set to ltr:

This tells the bidirectional algorithm "Leave me left-to-right!" and would produce the desired presentation:

english1 2WERBEH english3
4WERBEH english5 6WERBEH

The bdo element should be used in scenarios where absolute control over sequence order is required (e.g., multi-language part numbers). The
dir attribute is mandatory for this element.

Authors may also use special Unicode characters to override the bidirectional algorithm -- LEFT-TO-RIGHT OVERRIDE (202D) or RIGHT-TO-LEFT OVERRIDE (hexadecimal 202E). The POP DIRECTIONAL
FORMATTING (hexadecimal 202C) character ends either bidirectional override.

Note. Recall that conflicts can arise if the dir attribute is used on inline elements (including bdo concurrently with the corresponding [UNICODE] formatting characters.

Bidirectionality and character encodingAccording to [RFC1555] and [RFC1556], there are special conventions for the use of "charset" parameter values to indicate bidirectional treatment in MIME mail, in particular to distinguish
between visual, implicit, and explicit directionality. The parameter value "ISO-8859-8" (for Hebrew) denotes visual encoding, "ISO-8859-8-i" denotes implicit bidirectionality, and "ISO-8859-8-e"
denotes explicit directionality.

Because XHTML uses the Unicode bidirectionality algorithm, conforming documents encoded using ISO 8859-8 must be labeled as "ISO-8859-8-i". Explicit directional control is also possible with
HXTML, but cannot be expressed with ISO 8859-8, so "ISO-8859-8-e" should not be used.

The value "ISO-8859-8" implies that the document is formatted visually, misusing some markup (such as table with right alignment
and no line wrapping) to ensure reasonable display on older user agents that do not handle bidirectionality. Such documents do not conform to the present specification. If necessary, they can be made
to conform to the current specification (and at the same time will be displayed correctly on older user agents) by adding bdo markup where
necessary.Contrary to what is said in [RFC1555] and [RFC1556], ISO-8859-6
(Arabic) is not visual ordering.

Since ambiguities sometimes arise as to the directionality of certain characters (e.g., punctuation), the [UNICODE] specification includes
characters to enable their proper resolution. Also, Unicode includes some characters to control joining behavior where this is necessary (e.g., some situations with Arabic letters). XHTML includes
character references for these characters.

The zwnj entity is used to block joining behavior in contexts where joining will occur but shouldn't. The zwj entity does the opposite; it forces joining when it wouldn't
occur but should. For example, the Arabic letter "HEH" is used to abbreviate "Hijri", the name of the Islamic calendar system. Since the isolated form of "HEH" looks like the digit five as employed
in Arabic script (based on Indic digits), in order to prevent confusing "HEH" as a final digit five in a year, the initial form of "HEH" is used. However, there is no following context (i.e., a
joining letter) to which the "HEH" can join. The zwj character provides that context.

Similarly, in Persian texts, there are cases where a letter that normally would join a subsequent letter in a cursive connection should not. The character zwnj is used to block
joining in such cases.

The other characters, lrm and rlm, are used to force directionality of directionally neutral characters. For example, if a double quotation mark comes between an Arabic
(right-to-left) and a Latin (left-to-right) letter, the direction of the quotation mark is not clear (is it quoting the Arabic text or the Latin text?). The lrm and rlm
characters have a directional property but no width and no word/line break property. Please consult [UNICODE] for more details.

Mirrored character glyphs. In general, the bidirectional algorithm does not mirror character glyphs but leaves them unaffected. An exception are characters such as parentheses
(see [UNICODE], table 4-7). In cases where mirroring is desired, for example for Egyptian Hieroglyphs, Greek Bustrophedon, or special design
effects, this should be controlled with styles.

In general, using style sheets to change an element's visual rendering from block-level to inline or vice-versa is straightforward. However, because the bidirectional algorithm relies on the
inline/block-level distinction, special care must be taken during the transformation.

When an inline element that does not have a dir attribute is transformed to the style of a block-level element by a style sheet, it inherits
the dir attribute from its closest parent block element to define the base direction of the block.

When a block element that does not have a dir attribute is transformed to the style of an inline element by a style sheet, the resulting
presentation should be equivalent, in terms of bidirectional formatting, to the formatting obtained by explicitly adding a dir attribute
(assigned the inherited value) to the transformed element.

The Client-side Image Map Module provides elements for client side image maps. It requires that the Image Module (or another module that supports the img element) be included. The
Client-side Image Map Module supports the following elements:

This attribute specifies the position and shape on the screen. The number and order of values depends on the shape being defined. Possible combinations:

rect: left-x, top-y, right-x, bottom-y.

circle: center-x, center-y, radius. Note. When the radius value is a percentage value, user agents should calculate the final radius value based on the associated
object's width and height. The radius should be the smaller value of the two.

poly: x1, y1, x2, y2, ..., xN, yN. The first x and y coordinate pair and the last should be the same to close the polygon. When these coordinate values are not the same, user agents
should infer an additional coordinate pair to close the polygon.

Coordinates are relative to the top, left corner of the object. All values are of type Length. All values are separated by
commas.

This attribute specifies the position of the current element in the navingation order for the current document. This value must be a number between 0 and 32767. User agents must ignore leading
zeros.

The navigation order defines the order in which elements will receive focus when navigated by the user via the keyboard. The navigation order may
include elements nested within other elements.

Elements that may receive focus should be navigated by user agents according to the following rules:

Those elements that support the navindex attribute and assign a positive value to it are navigated first. Navigation proceeds
from the element with the lowest navindex value to the element with the highest value. Values need not be sequential nor must they
begin with any particular value. Elements that have identical navindex values should be navigated in the order they appear in the
character stream.

Those elements that do not support the navindex attribute or support it and assign it a value of "0" are navigated next. These
elements are navigated in the order they appear in the character stream.

Elements that are disabled do not participate in the navigation order.

Tabbing keys. The actual key sequence that causes navigation or element activation depends on the configuration of the user agent (e.g., the "tab" key is used for navigation
and the "enter" key is used to activate a selected element).

User agents may also define key sequences to navigate the navigation order in reverse. When the end (or beginning) of the navigation order is reached, user agents may circle back to the
beginning (or end).

This attribute assigns an access key to an element. An access key is a single character from the document character set. Note.
Authors should consider the input method of the expected reader when specifying an accesskey.

Pressing an access key assigned to an element gives focus to the element. The action that occurs when an element receives focus depends on the
element. For example, when a user activates a link defined by the a element, the user agent generally follows the link. When a user
activates a radio button, the user agent changes the value of the radio button. When the user activates a text field, it allows input, etc.

In this example, we assign an access key to a link defined by the a element. Typing this access key takes the user to another
document, in this case, a table of contents.

The invocation of access keys depends on the underlying system. For instance, on machines running MS Windows, one generally has to press the "alt" key in addition to the access key. On Apple
systems, one generally has to press the "cmd" key in addition to the access key.

The rendering of access keys depends on the user agent. We recommend that authors include the access key in label text or wherever the access key is to apply. User agents should render the value
of an access key in such a way as to emphasize its role and to distinguish it from other characters (e.g., by underlining it).

For user agents that cannot display images, forms, or applets, this attribute specifies alternate text. The language of the alternate text is specified by the xml:lang attribute.

Several non-textual elements let authors specify alternate text to serve as content when the element cannot be rendered normally. Specifying alternate text assists users without graphic display
terminals, users whose browsers don't support forms, visually impaired users, those who use speech synthesizers, those who have configured their graphical user agents not to display images, etc.

While alternate text may be very helpful, it must be handled with care. Authors should observe the following guidelines:

Do not specify irrelevant alternate text when including images intended to format a page, for instance, alt="red ball" would be inappropriate for an image that adds a red
ball for decorating a heading or paragraph. In such cases, the alternate text should be the empty string (""). Authors are in any case advised to avoid using images to format pages; style sheets
should be used instead.

Do not specify meaningless alternate text (e.g., "dummy text"). Not only will this frustrate users, it will slow down user agents that must convert text to speech or braille output.

The map element specifies a client-side image map (or other navigation mechanism) that may be associated with another object. An
image map is associated with an element via the element's usemap attribute. The map element may be used without an associated image for general navigation mechanisms.

The presence of the usemap attribute for an object implies that the
object being included is an image. Furthermore , when the object element has an
associated client-side image map, user agents may implement user interaction with the object solely in terms of the client-side image
map. This allows user agents (such as an audio browser or robot) to interact with the object without having to process it; the user agent
may even elect not to retrieve (or process) the object. When an object has an associated image map, authors should not expect that the
object will be retrieved or processed by every user agent.

One or more area elements. These elements have no content but specify the geometric regions of the image map and the link
associated with each region. Note that user agents do not generally render area elements. Therefore, authors must provide alternate
text for each area with the alt attribute.

Block-level content. This content should include a elements that specify the geometric regions of the image map and the link
associated with each region. Note that the user agent should render block-level content of a map element. Authors should use this method
to create more accessible documents.

When a map element contains mixed content (both area elements and
block-level content), user agents must ignore the area elements.

Authors should specify an image maps's geometry completely with area elements, or completely with a elements, or completely with both if content is mixed. Authors may wish to mix content so that older user agents will handle map geometries specified by area elements and new user agents will take advantage of richer block content.

User agents and authors should offer textual alternates to graphical image maps for cases when graphics are not available or the user cannot
access them. For example, user agents may use alt text to create textual links in place of a graphical image map. Such links may be
activated in a variety of ways (keyboard, voice activation, etc.).

In the following example, we create a client-side image map for the object element. We do not want to render the image map's contents
when the object is rendered, so we "hide" the map element within the object element's content. Consequently, the map element's contents will only
be rendered if the object cannot be rendered.

We may want to render the image map's contents even when a user agent can render the object. For instance, we may want to associate an
image map with an object element and include a text navigation bar at the bottom of the page. To do so, we define the map element outside the object:

If the user agent doesn't support the PNG format, it tries to render the GIF image. If it doesn't support GIF (e.g., it's a speech-based user agent), it defaults to the text description provided
as the content of the inner object element. When object elements are nested
this way, authors may share image maps among them:

The following example illustrates how anchors may be specified to create inactive zones within an image map. The first anchor specifies a small circular region with no associated link. The second
anchor specifies a larger circular region with the same center coordinates. Combined, the two form a ring whose center is inactive and whose rim is active. The order of the anchor definitions is
important, since the smaller circle must override the larger circle.

The del element is used to indicate that a section of a document has been deleted with respect to a different version of the document (e.g.,
in draft legislation where lawmakers need to view the changes).

The value of this attribute is a URI that designates a source document or message. This attribute is intended to give further information about the element's contents (e.g., the source from which
a quotation was borrowed, or the reason text was inserted or deleted). User Agents should provide a means for the user to access the further information.

The value of this attribute specifies the date and time when a change was made.

This element is unusual for XHTML in that they may serve as either block-level or inline elements (but not both). It may contain one or more words within a paragraph or contain one or more
block-level elements such as paragraphs, lists and tables.

This example could be from a bill to change the legislation for how many deputies a County Sheriff can employ from 3 to 5.

<p>
A Sheriff can employ <del>3</del><ins>5</ins> deputies.
</p>

The del element must not contain block-level content when it is behaving as an inline element.

ILLEGAL EXAMPLE:
The following is not legal HTML.

<p>
<ins><div>...block-level content...</div></ins>
</p>

User agents should render deleted text in ways that make the change obvious. For instance, inserted text may appear in a special font, deleted text may not be shown at all or be shown as
struck-through or with special markings, etc.

Both of the following examples correspond to November 5, 2001, 8:15:30 am, US Eastern Standard Time.

<ins datetime="2001-11-05T08:15:30-05:00"
cite="http://www.example.org/mydoc/comments.html">
Furthermore, the latest figures from the marketing department
suggest that such practice is on the rise.
</ins>

The document "http://www.example.org/mydoc/comments.html" would contain comments about why information was inserted into the document.

Authors may also make comments about deleted text by means of the title attribute for the del element. User agents may present this information to the user (e.g., as a popup note). For example:

<del datetime="2001-11-05T08:15:30-05:00"
title="Changed as a result of Steve G's comments in meeting.">
Furthermore, the latest figures from the marketing department
suggest that such practice is on the rise.
</del>

The ins element is used to indicate that a section of a document has been inserted with respect to a different version of the document (e.g.,
in draft legislation where lawmakers need to view the changes).

The value of this attribute is a URI that designates a source document or message. This attribute is intended to give further information about the element's contents (e.g., the source from which
a quotation was borrowed, or the reason text was inserted or deleted). User Agents should provide a means for the user to access the further information.

The value of this attribute specifies the date and time when a change was made.

This element is unusual for XHTML in that they may serve as either block-level or inline elements (but not both). It may contain one or more words within a paragraph or contain one or more
block-level elements such as paragraphs, lists and tables.

The ins element must not contain block-level content when it is behaving as an inline element.

ILLEGAL EXAMPLE:
The following is not legal HTML.

<p>
<ins><div>...block-level content...</div></ins>
</p>

User agents should render inserted text in ways that make the change obvious. For instance, inserted text may appear in a special font.

Both of the following examples correspond to November 5, 2001, 8:15:30 am, US Eastern Standard Time.

<ins datetime="2001-11-05T08:15:30-05:00"
cite="http://www.foo.org/mydoc/comments.html">
Furthermore, the latest figures from the marketing department
suggest that such practice is on the rise.
</ins>

The document "http://www.foo.org/mydoc/comments.html" would contain comments about why information was inserted into the document.

Authors may also make comments about inserted text by means of the title attribute for the ins element. User agents may present this information to the user (e.g., as a popup note). For example:

<ins datetime="2001-11-05T08:15:30-05:00"
title="Changed as a result of Steve B's comments in meeting.">
Furthermore, the latest figures from the marketing department
suggest that such practice is on the rise.
</ins>

The Link Module defines an element that can be used to define links to external resources. These resources are often used to augment the user agent's ability to process the associated XHTML
document. The element and attributes included in this module are:

This attribute gives an advisory hint as to the content type of the content available at the link target address. It allows user agents to opt to use a fallback mechanism rather than fetch the
content if they are advised that they will get content in a content type they do not support.

Authors who use this attribute take responsibility to manage the risk that it may become inconsistent with the content available at the link target address.

For the current list of registered content types, please consult [MIMETYPES].

This element defines a link. Unlike a, it may only appear in the
head section of a document, although it may appear any number of times. Although link has no content, it conveys relationship information
that may be rendered by user agents in a variety of ways (e.g., a tool-bar with a drop-down menu of links).

This example illustrates how several link definitions may appear in the
head section of a document. The current document is "Chapter2.html". The rel attribute specifies the relationship of the linked document
with the current document. The values "Index", "Next", and "Prev" are explained in the section on link types.

When the link element links an external style sheet to a document, the type
attribute specifies the style sheet language and the media attribute specifies the intended rendering medium or media. User agents may save
time by retrieving from the network only those style sheets that apply to the current device.

Authors may use the link element to provide a variety of information to search engines, including:

Links to alternate versions of a document, written in another human language.

Links to alternate versions of a document, designed for different media, for instance a version especially suited for printing.

Links to the starting page of a collection of documents.

The examples below illustrate how language information, media types, and link types may be combined to improve document handling by search engines.

The following example shows how to use the hreflang attribute to indicate to a search engine where to find Dutch, Portuguese, and Arabic
versions of a document. Note the use of the charset attribute for the Arabic manual. Note also the use of the xml:lang attribute to indicate that the value of the title attribute for the link element designating the French manual is in
French.

This attribute may be used in place of the name attribute. HTTP servers use this attribute to gather information for HTTP response message
headers.

The meta element can be used to identify properties of a document (e.g., author, expiration date, a list of key words, etc.) and assign
values to those properties. This specification does not define a normative set of properties.

Each meta element specifies a property/value pair. The name attribute identifies the
property and the content attribute specifies the property's value.

For example, the following declaration sets a value for the Author property:

<meta name="Author" content="Dave Raggett"/>

The xml:lang attribute can be used with meta
to specify the language for the value of the content attribute. This enables speech synthesizers to apply language dependent pronunciation
rules.

In this example, the author's name is declared to be French:

<meta name="Author" lang="fr" content="Arnaud Le Hors"/>

Note. The meta element is a generic mechanism for specifying meta data. However, some XHTML elements and attributes
already handle certain pieces of meta data and may be used by authors instead of meta to specify those pieces: the title element, the address element, the
ins and del elements, the title attribute, and
the cite attribute.

Note. When a property specified by a meta element takes a value that is a URI, some authors prefer to specify the meta data via the link element. Thus, the following meta data declaration:

A common use for meta is to specify keywords that a
search engine may use to improve the quality of search results. When several meta elements provide language-dependent information
about a document, search engines may filter on the xml:lang attribute to display search results using the
language preferences of the user. For example,

The effectiveness of search engines can also be increased by using the link element to specify links to translations of the document in
other languages, links to versions of the document in other media (e.g., PDF), and, when the document is part of a collection, links to an appropriate starting point for browsing the collection.

The Platform for Internet Content Selection
(PICS, specified in [PICS]) is an infrastructure for associating labels (meta data) with Internet content. Originally designed to help parents and
teachers control what children can access on the Internet, it also facilitates other uses for labels, including code signing, privacy, and intellectual property rights management.

This example illustrates how one can use a meta declaration to include a PICS 1.1 label:

As a globally unique name. User agents may be able to recognize the name (without actually retrieving the profile) and perform some activity based on known conventions for that profile. For
instance, search engines could provide an interface for searching through catalogs of HTML documents, where these documents all use the same profile for representing catalog entries.

As a link. User agents may dereference the URI and perform some activity based on the actual definitions within the profile (e.g., authorize the usage of the profile within the current HTML
document). This specification does not define formats for profiles.

This example refers to a hypothetical profile that defines useful properties for document indexing. The properties defined by this profile -- including "author", "copyright", "keywords", and
"date" -- have their values set by subsequent meta declarations.

This attribute specifies a comma-separated list of URIs for archives containing classes and other resources that will be "preloaded". The classes are loaded using an instance of an
AppletClassLoader with the given codebase. Relative URIs for archives are interpreted with respect to the applet's codebase. Preloading
resources can significantly improve the performance of applets.

This attribute may be used to specify the location of an object's implementation via a URI. It may be used together with, or as an alternative to the data attribute, depending on the type of object involved.

This attribute specifies the base URI for the applet. If this attribute is not specified, then it defaults the same base URI as for the current document. Values for this attribute may only refer
to subdirectories of the directory containing the current document.

This attribute specifies the content type of data expected when downloading the object specified by classid. This attribute is
optional but recommended when classid is specified since it allows the user agent to avoid loading information for unsupported content
types. When absent, it defaults to the value of the type attribute.

This attribute may be used to specify the location of the object's data, for instance image data for objects defining images, or more generally, a serialized form of an object which can be used
to recreate it. If given as a relative URI, it should be interpreted relative to the codebase attribute.

This attribute specifies the position of the current element in the navingation order for the current document. This value must be a number between 0 and 32767. User agents must ignore leading
zeros.

The navigation order defines the order in which elements will receive focus when navigated by the user via the keyboard. The navigation order may
include elements nested within other elements.

Elements that may receive focus should be navigated by user agents according to the following rules:

Those elements that support the navindex attribute and assign a positive value to it are navigated first. Navigation proceeds from
the element with the lowest navindex value to the element with the highest value. Values need not be sequential nor must they begin
with any particular value. Elements that have identical navindex values should be navigated in the order they appear in the character
stream.

Those elements that do not support the navindex attribute or support it and assign it a value of "0" are navigated next. These
elements are navigated in the order they appear in the character stream.

Elements that are disabled do not participate in the navigation order.

Tabbing keys. The actual key sequence that causes navigation or element activation depends on the configuration of the user agent (e.g., the "tab" key is used for navigation
and the "enter" key is used to activate a selected element).

User agents may also define key sequences to navigate the navigation order in reverse. When the end (or beginning) of the navigation order is reached, user agents may circle back to the
beginning (or end).

This attribute gives an advisory hint as to the content type of the content available at the link target address. It allows user agents to opt to use a fallback mechanism rather than fetch the
content if they are advised that they will get content in a content type they do not support.

Authors who use this attribute take responsibility to manage the risk that it may become inconsistent with the content available at the link target address.

For the current list of registered content types, please consult [MIMETYPES].

Most user agents have built-in mechanisms for processing common data types such as text, GIF images, colors, fonts, and a handful of graphic
elements. To process data types they don't support natively, user agents generally run external applications. The object element allows
authors to control whether data should be processed externally or by some program, specified by the author, that processes the data within the user agent.

In the most general case, an author may need to specify three types of information:

The implementation of the included object. For instance, if the included object is a clock applet, the author must indicate the location of the applet's executable code.

The data to be processed. For instance, if the included object is a program that processes font data, the author must indicate the location of that data.

Additional values required by the object at run-time. For example, some applets may require initial values for parameters.

The object element allows authors to specify all three types of data, but authors may not have to specify all three at once. For
example, some objects may not require data (e.g., a self-contained applet that performs a small animation). Others may not require run-time initialization. Still others may not require additional
implementation information, i.e., the user agent itself may already know how to process that type of data (e.g., GIF images).

Theobject element may also appear in the content of the head element. Since user agents generally do not process elements in the head, authors
should ensure that any object elements in the head do not specify
content that may be processed. Please consult the section on sharing frame data for an example of including the object element in the head element.

Please consult the section on form controls for information about object elements in forms.

This document does not specify the behavior of object elements that use both the classid attribute to identify an implementation and the data attribute to specify data for that
implementation. In order to ensure portability, authors should use the param element to tell implementations where to retrieve additional
data.

A user agent must interpret an object element according to the following precedence rules:

The user agent must first try to process the object. It should not process the element's contents, but it must examine them in case the element contains any direct children that are param elements (see object initialization) or map elements (see client-side image maps).

If the user agent is not able to process the object for whatever reason (configured not to, lack of resources, wrong architecture, etc.), it must try to process its contents.

In the following example, we insert an analog clock applet in a document via the object element. The applet, written in the Python
language, requires no additional data or run-time values. The classid attribute specifies the location of the applet:

<object classid="http://www.miamachina.it/analogclock.py">
</object>

Note that the clock will be processed as soon as the user agent interprets this object declaration. It is possible to delay processing
of an object by first declaring the object (described below).

Authors should complete this declaration by including alternate text as the contents of object in case the user agent cannot process
the clock.

One significant consequence of the object element's design is that it offers a
mechanism for specifying alternate object processing; each embedded object declaration may specify alternate content types. If a user
agent cannot process the outermost object, it tries to process the contents, which may be another object element, etc.

In the following example, we embed several object declarations to illustrate how alternate processing work. A user agent will attempt
to process the first object element it can, in the following order: (1) an Earth applet written in the Python language, (2) an MPEG
animation of the Earth, (3) a GIF image of the Earth, (4) alternate text.

The outermost declaration specifies an applet that requires no data or initial values. The second declaration specifies an MPEG animation and, since it does not define the location of an
implementation to handle MPEG, relies on the user agent to handle the animation. We also set the type attribute so that a user agent that
knows it cannot process an MPEG will not bother to retrieve "TheEarth.mpeg" from the network. The third declaration specifies the location of a GIF file and furnishes alternate text in case all other
mechanisms fail.

Inline vs. external data. Data to be processed may be supplied in two ways: inline and from an external resource. While the former method will generally lead to faster
processing, it is not convenient when processing large quantities of data.

Here's an example that illustrates how inline data may be fed to an object:

data: This is default value for the attribute. It means that the value specified by value will be evaluated and
passed to the object's implementation as a string.

ref: The value specified by value is a URI that designates a resource where run-time values are stored. This allows
support tools to identify URIs given as parameters. The URI must be passed to the object as is, i.e., unresolved.

object: The value specified by value is an identifier that refers to an object declaration in the same document. The identifier must be the value of the id attribute set for the declared object element.

This attribute specifies the content type of the resource designated by the value attribute only in the case
where valuetype is set to "ref". This attribute thus specifies for the user agent, the type of values that will be found at the URI
designated by value.

param elements specify a set of values that may be required by an object at run-time. Any number of param elements may appear in the content of an object element, in any order, but must be placed
at the start of the content of the enclosing object element.

The syntax of names and values is assumed to be understood by the object's implementation. This document does not specify how user agents should retrieve name/value pairs nor how they should
interpret parameter names that appear twice.

We return to the clock example to illustrate the use of param: suppose that the applet is able to handle two run-time parameters that
define its initial height and width. We can set the initial dimensions to 40x40 pixels with two param.

In the following example, run-time data for the object's "Init_values" parameter is specified as an external resource (a GIF file). The value of the valuetype attribute is thus set to "ref" and the value is a URI designating the
resource.

Note that we have also set the standby attribute so that the user agent may display a message while the rendering mechanism
loads.

When an object element is rendered, user agents must search the content for only those param elements that are direct children and "feed" them to the object.

Thus, in the following example, if "obj1" is rendered, "param1" applies to "obj1" (and not "obj2"). If "obj1" is not rendered and "obj2" is, "param1" is ignored, and "param2" applies to "obj2". If
neither object is rendered, neither param applies.

The location of an object's implementation is given by a URI. The first segment of an absolute URI specifies the naming scheme used to transfer the data designated by the URI. For XHTML documents,
this scheme is frequently "http". Some applets might employ other naming schemes. For instance, when specifying a Java applet, authors may use URIs that begin with "java" and for ActiveX applets,
authors may use "clsid".

In the following example, we insert a Java applet into an XHTML document.

<p><object classid="java:program.start">
</object>

By setting the codetype attribute, a user agent can decide whether to retrieve the Java application based on its ability to do
so.

Some rendering schemes require additional information to identify their implementation and must be told where to find that information. Authors may give path information to the object's
implementation via the codebase attribute.

The preceding examples have only illustrated isolated object definitions. When a document is to contain more than one instance of the same object, it is possible to separate the declaration of the
object from its instantiations. Doing so has several advantages:

Data may be retrieved from the network by the user agent one time (during the declaration) and reused for each instantiation.

It is possible to instantiate an object from a location other than the object's declaration, for example, from a link.

It is possible to specify objects as run-time data for other objects.

To declare an object so that it is not executed when read by the user agent, set the boolean declare attribute in the object element. At the same time, authors must identify the declaration by setting the id attribute in the object element to a unique value. Later
instantiations of the object will refer to this identifier.

A declared object must appear in a document before the first instance of that object.

An object defined with the declare attribute is instantiated every time an element that refers to that object requires it to be
rendered (e.g., a link that refers to it is activated, an object that refers to it is activated, etc.).

In the following example, we declare an object and cause it to be instantiated by referring to it from a link. Thus, the object can be
activated by clicking on some highlighted text, for example.

<p><object declare
id="earth.declaration"
data="TheEarth.mpeg"
type="application/mpeg">
The <strong>Earth</strong> as seen from space.
</object>
...later in the document...
<p>A neat <A href="#earth.declaration"> animation of The Earth!</A>

The following example illustrates how to specify run-time values that are other objects. In this example, we send text (a poem, in fact) to a hypothetical mechanism for viewing poems. The object
recognizes a run-time parameter named "font" (say, for rendering the poem text in a certain font). The value for this parameter is itself an object that inserts (but does not render) the font object.
The relationship between the font object and the poem viewer object is achieved by (1) assigning the id
"tribune" to the font object declaration and (2) referring to it from the param element of the poem viewer object (with valuetype and value).

The Scripting Module defines elements that are used to contain information pertaining to executable scripts or the lack of support for executable scripts. Elements and attributes included in this
module are:

When this module is used, the script and noscript elements
are added to the Block and Inline content sets of the Text Module. In addition, the script element is added to the content model of
the head element defined in the Structure Module.

A collection of attributes related to Internationalization, including the xml:lang.

The noscript element allows authors to provide alternate content when a script is not executed. The content of a noscript element should only be rendered by a script-aware user agent in the following cases:

The user agent is configured not to evaluate scripts.

The user agent doesn't support a scripting language invoked by a script element earlier in the document.

The user agent can't access an external script.

User agents that do not support client-side scripts must render this element's contents.

In the following example, a user agent that executes the script will include some dynamically created data in the document. If
the user agent doesn't support scripts, the user may still retrieve the data through a link.

This attribute gives an advisory hint as to the content type of the content available at the link target address. It allows user agents to opt to use a fallback mechanism rather than fetch the
content if they are advised that they will get content in a content type they do not support.

Authors who use this attribute take responsibility to manage the risk that it may become inconsistent with the content available at the link target address.

For the current list of registered content types, please consult [MIMETYPES].

Attribute defer not found

The attribute defer was not able to be loaded by the document generator. This implies that either 1) the attribute is not yet defined, or 2) the name is incorrect.

This attribute specifies the character encoding of the resource designated by the link. Please consult the section on character encodings for more details.

The script element places a script within a document. This element may appear any number of times in the head or body of an XHTML document.

The script may be defined within the contents of the script element or in an external file. If the src attribute is not set, user agents must interpret the contents of the element as the script. If the src has a URI value, user agents must ignore the element's contents and retrieve the script via the URI. Note that the charset attribute refers to the character encoding of the script designated by
the src attribute; it does not concern the content of the script
element.

Scripts are evaluated by script engines that must be known to a user agent.

As XHTML does not rely on a specific scripting language, document authors must explicitly tell user agents the language of each script. This may be done either through a default declaration or a
local declaration.

The type attribute must be specified for each script element
instance in a document.

In this example, we include one script in the header, whose script is located in an external file and is in the scripting
language "text/vbscript". We also include one script in the body, which contains its own script written in "text/javascript".

Scripts that are executed when a document is loaded may be able to modify the document's contents dynamically. The ability to do so depends on the scripting language itself (e.g., the
"document.write" statement in the XHTML object model supported by some vendors).

The Server-side Image Map Module provides support for image-selection and transmission of selection coordinates. It requires that the Object Module (or another module that supports the object element) be included. The Server-side Image Map Module supports the following attributes:

This attribute indicates that the associated element is to be treated as a "server-side image map". When selected, the coordinates within the element that the user selected are sent to the server
where the document resides. Screen coordinates are expressed as screen pixel values relative to the image.

In the following example, the active region defines a server-side link. Thus, a click anywhere on the image will cause the click's coordinates to be sent to the server.

The location clicked is passed to the server as follows. The user agent derives a new URI from the URI specified by the href attribute of the a element, by appending `?' followed by the x
and y coordinates, separated by a comma. The link is then followed using the new URI. For instance, in the given example, if the user clicks at the location x=10, y=27 then the derived URI is
"http://www.example.com/cgi-bin/competition?10,27".

User agents that do not offer the user a means to select specific coordinates (e.g., non-graphical user agents that rely on keyboard input, speech-based user agents, etc.) should send the
coordinates "0,0" to the server when the link is activated.

This attribute gives an advisory hint as to the content type of the content available at the link target address. It allows user agents to opt to use a fallback mechanism rather than fetch the
content if they are advised that they will get content in a content type they do not support.

Authors who use this attribute take responsibility to manage the risk that it may become inconsistent with the content available at the link target address.

For the current list of registered content types, please consult [MIMETYPES].

The style element allows an author to put style sheet rules in the head of
the document. XHTML permits any number of style elements in the
head section of a document.

User agents that don't support style sheets, or don't support the specific style sheet language used by a style element, must
hide the contents of the style element. It is an error to render the content as
part of the document's text.

The syntax of style data depends on the style sheet language.

Rules for style rule precedences and inheritance depend on the style sheet language.

The following CSS style declaration puts a border around every h1
element in the document and centers it on the page.

Although style information may be set for almost every XHTML element, two elements, div
and span, are particularly useful in that they do not impose any presentation semantics (besides block-level vs. inline). When combined with
style sheets, these elements allow users to extend XHTML indefinitely, particularly when used with the class
and id attributes.

In the following example, we use the span element to set the font style of the first few words of a paragraph to small caps.

In the following example, we use div and the class
attribute to set the text justification for a series of paragraphs that make up the abstract section of a scientific article. This style information could be reused for other abstract sections by
setting the class attribute elsewhere in the document.

<head>
<style type="text/css">
div.Abstract { text-align: justify }
</style>
</head>
<body>
<div class="Abstract">
<p>The Chieftain product range is our market winner for
the coming year. This report sets out how to position
Chieftain against competing products.</p>
<p>Chieftain replaces the Commander range, which will
remain on the price list until further notice.</p>
</div>
</body>

Authors may group several alternate style sheets (including the author's preferred style sheets) under a single style name. When a user selects a named style, the user agent must apply
all style sheets with that name. User agents must not apply alternate style sheets with a different style name. The section on specifying external style sheets explains how to name a group of style
sheets.

Authors specify external style sheets with the following attributes of the link element:

Set the value of href to the location of the style sheet file. The value of href is
a URI.

Set the value of the type attribute to indicate the language of the linked (style sheet) resource. This allows the user agent
to avoid downloading a style sheet for an unsupported style sheet language.

Specify that the style sheet is persistent, preferred, or alternate:

To make a style sheet persistent, set the rel attribute to "stylesheet" and don't set the title attribute.

To make a style sheet preferred, set the rel attribute to "stylesheet" and name the style sheet with the title attribute.

To specify an alternate style sheet, set the rel attribute to "alternate stylesheet" and name the style sheet with the title attribute.

User agents should provide a means for users to view and pick from the list of alternate styles. The value of the title attribute is recommended as the name of each choice.

In this example, we first specify a persistent style sheet located in the file mystyle.css:

<link href="mystyle.css" rel="stylesheet" type="text/css"/>

Setting the title attribute makes this the author's preferred style sheet:

As its name suggests, the Tables Module provides table-related elements that are updated to enable access by non-visual user agents. Specifically, the Tables Module supports the following
elements, attributes, and content model:

The following text was included in HTML 4 - should we make this a "MUST" in XHTML 2 for visual user agents?

Visual user agents should avoid clipping any part of the table including the caption, unless a means is provided to access all parts, e.g., by
horizontal or vertical scrolling. We recommend that the caption text be wrapped to the same width as the table.

This attribute, which must be an integer > 0, and the default value for this attribute is 1. This specifies the number of columns in a colgroup, or specifies the number of columns "spanned" by the col element.

Values mean the following:

In the absence of a span attribute, each colgroup defines a column
group containing one column.

If the span attribute is used with the colgroup element and the value
is set to N > 0, that defines a column group containing N columns.

If the span attribute is used with the col element and the value is set to
to N > 1, the current col element shares its attributes with the next N-1 columns.

User agents must ignore this attribute if the colgroup element contains one or more col elements.

The colgroup element allows authors to create structural divisions within a table. Authors may highlight this structure through
style sheets.

A table may either contain a single implicit column group (no colgroup
element delimits the columns) or any number of explicit column groups (each delimited by an instance of the colgroup element).

The col element allows authors to share attributes among several columns without implying any structural grouping. The "span" of the col element is the number of columns that will share the element's attributes.

The colgroup element creates an explicit column group. The number of columns in the column group may be specified in two, mutually
exclusive ways:

The element's span attribute (default value 1) specifies the number of columns in the group.

Each col element in the colgroup represents one or more columns in the
group.

The advantage of using the colgroup attribute is that authors may group information about multiple columns.

When it is necessary to single out a column (e.g., for style information, to specify width information, etc.) within a group, authors must identify that column with a col element.

The col element allows authors to group together attribute specifications for table columns. The col does not group columns together structurally -- that is the role of the
colgroup element. col elements are empty and serve only as a support for attributes. They may appear inside or outside an explicit
column group (i.e., colgroup element).

The direction of text in individual cells can be changed by setting the dir attribute in an element that defines the cell. Please consult the
section on bidirectional text for more information on text direction issues.

Non-visual user agents such as speech synthesizers and Braille-based devices may use the following td and th element attributes to render table cells more intuitively:

For a given data cell, the headers attribute lists which cells provide pertinent header information. For this purpose, each header
cell must be named using the id attribute. Note that it's not always possible to make a clean division of cells
into headers or data. You should use the td element for such cells together with the id or scope attributes as appropriate.

For a given header cell, the scope attribute tells the user agent the data cells for which this header provides information. Authors may choose to use this attribute instead of headers according to which is more convenient; the two attributes fulfill the same function. The headers attribute is generally needed when headers are placed in irregular positions with respect to the data they apply to.

The abbr attribute specifies an abbreviated header for header cells
so that user agents may render header information more rapidly.

In the following example, we assign header information to cells by setting the headers attribute. Each cell in the same column refers
to the same header cell (via the id attribute).

Caption: Cups of coffee consumed by each senator
Summary: This table charts the number of cups
of coffee consumed by each senator, the type
of coffee (decaf or regular), and whether
taken with sugar.
Name: T. Sexton, Cups: 10, Type: Espresso, Sugar: No
Name: J. Dinnen, Cups: 5, Type: Decaf, Sugar: Yes

Note how the header "Type of Coffee" is abbreviated to "Type" using the abbr attribute.

Here is the same example substituting the scope attribute for the
headers attribute. Note the value "col" for the scope attribute, meaning "all cells in the current column":

Note the use of the scope attribute with the "row" value. Although the first cell in each row contains data, not header information,
the scope attribute makes the data cell behave like a row header cell. This allows speech synthesizers to provide the relevant course name
upon request or to state it immediately before each cell's content.

Users browsing a table with a speech-based user agent may wish to hear an explanation of a cell's contents in addition to the contents themselves. One way the user might provide an explanation is
by speaking associated header information before speaking the data cell's contents (see the section on associating header information with data cells).

Users may also want information about more than one cell, in which case header information provided at the cell level (by headers, scope, and abbr) may not provide adequate context. Consider the following table,
which classifies expenses for meals, hotels, and transport in two locations (San Jose and Seattle) over several days:

Users might want to extract information from the table in the form of queries:

"What did I spend for all my meals?"

"What did I spend for meals on 25 August?"

"What did I spend for all expenses in San Jose?"

Each query involves a computation by the user agent that may involve zero or more cells. In order to determine, for example, the costs of meals on 25 August, the user agent must know which table
cells refer to "Meals" (all of them) and which refer to "Dates" (specifically, 25 August), and find the intersection of the two sets.

To accommodate this type of query, the table model allows authors to place cell headers and data into categories. For example, for the travel expense table, an author could group the header cells
"San Jose" and "Seattle" into the category "Location", the headers "Meals", "Hotels", and "Transport" in the category "Expenses", and the four days into the category "Date". The previous three
questions would then have the following meanings:

"What did I spend for all my meals?" means "What are all the data cells in the "Expenses=Meals" category?

"What did I spend for meals on 25 August?" means "What are all the data cells in the "Expenses=Meals" and "Date=Aug-25-1997" categories?

"What did I spend for all expenses in San Jose?" means "What are all the data cells in the "Expenses=Meals, Hotels, Transport" and "Location=San Jose" categories?

Authors categorize a header or data cell by setting the axis attribute for the cell. For instance, in the travel expense table, the cell
containing the information "San Jose" could be placed in the "Location" category as follows:

<th id="a6" axis="location">San Jose</th>

Any cell containing information related to "San Jose" should refer to this header cell via either the headers or the scope attribute. Thus, meal expenses for 25-Aug-1997 should be marked up to refer to id attribute (whose value here is "a6") of the "San Jose" header cell:

<td headers="a6">37.74</td>

Each headers attribute provides a list of id
references. Authors may thus categorize a given cell in any number of ways (or, along any number of "headers", hence the name).

Note that marking up the table this way also allows user agents to avoid confusing the user with unwanted information. For instance, if a speech synthesizer were to speak all of the figures in the
"Meals" column of this table in response to the query "What were all my meal expenses?", a user would not be able to distinguish a day's expenses from subtotals or totals. By carefully categorizing
cell data, authors allow user agents to make important semantic distinctions when rendering.

Of course, there is no limit to how authors may categorize information in a table. In the travel expense table, for example, we could add the additional categories "subtotals" and "totals".

This specification does not require user agents to handle information provided by the axis attribute, nor does it make any
recommendations about how user agents may present axis information to users or how users may query the user agent about this
information.

However, user agents, particularly speech synthesizers, may want to factor out information common to
several cells that are the result of a query. For instance, if the user asks "What did I spend for meals in San Jose?", the user agent would first determine the cells in question (25-Aug-1997: 37.74,
26-Aug-1997:27.28), then render this information. A user agent speaking this information might read it:

This attribute should be used to provide an abbreviated form of the cell's content, and may be rendered by user agents when appropriate in place of the cell's content. Abbreviated names should be
short since user agents may render them repeatedly. For instance, speech synthesizers may render the abbreviated headers relating to a particular cell before rendering that cell's content.

This attribute may be used to place a cell into conceptual categories that can be considered to form axes in an n-dimensional space. User agents may give users access to these categories (e.g.,
the user may query the user agent for all cells that belong to certain categories, the user agent may present a table in the form of a table of contents, etc.). Please consult the section on categorizing cells for more information. The value of this attribute is a comma-separated list of category names.

This attribute specifies the number of columns spanned by the current cell. The default value of this attribute is one ("1"). The value zero ("0") means that the cell spans all columns from the
current column to the last column of the column group ( colgroup) in which the cell is defined.

This attribute specifies the list of header cells that provide header information for the current data cell. The value of this attribute is a space-separated list of cell names; those cells must
be named by setting their id attribute. Authors generally use the headers attribute to help non-visual user agents render header information about data cells (e.g., header information is spoken prior to the cell data), but
the attribute may also be used in conjunction with style sheets. See also the scope attribute.

This attribute specifies the number of rows spanned by the current cell. The default value of this attribute is one ("1"). The value zero ("0") means that the cell spans all rows from the current
row to the last row of the table section ( thead, tbody, or tfoot) in which the cell is defined.

This attribute specifies the set of data cells for which the current header cell provides header information. This attribute may be used in place of the headers attribute, particularly for simple tables. When specified, this attribute must have one of the following values:

row: The current cell provides header information for the rest of the row that contains it (see also the section on table
directionality).

col: The current cell provides header information for the rest of the column that contains it.

rowgroup: The header cell provides header information for the rest of the row group that contains it.

colgroup: The header cell provides header information for the rest of the column group that contains it.

Table cells may contain two types of information: header information and data. This distinction enables user agents to render header and data cells distinctly, even in the absence
of style sheets. For example, visual user agents may present header cell text with a bold font. Speech synthesizers may render header information with a distinct voice inflection.

The th element defines a cell that contains header information. User agents have two pieces of header information available: the contents
of the th element and the value of the abbr attribute. User agents must render
either the contents of the cell or the value of the abbr attribute. For visual media, the latter may be appropriate when there is
insufficient space to render the full contents of the cell. For non-visual media abbr may be used as an abbreviation for table headers when
these are rendered along with the contents of the cells to which they apply.

As cell "2" spans the first and second rows, the definition of the second row will take it into account. Thus, the second td in row two
actually defines the row's third cell. Visually, the table might be rendered to a tty device as:

Defining overlapping cells is an error. User agents may vary in how they handle this error (e.g., rendering may vary).

The following illegal example illustrates how one might create overlapping cells. In this table, cell "5" spans two rows and cell "7" spans two columns, so there is overlap in the cell between "7"
and "9":

Table rows may be grouped into a table head, table foot, and one or more table body sections,
using the thead, tfoot and tbody elements, respectively. This division enables user agents to support scrolling of table bodies independently of the table head and foot. When long tables
are printed, the table head and foot information may be repeated on each page that contains table data.

The table head and table foot should contain information about the table's columns. The table body should contain rows of table data.

When present, each thead, tfoot, and tbody contains a row group. Each row group must contain at least one row, defined by the tr
element.

If the thead, tfoot, and tbody elements are used, and a rowspan attriubte is used within a group, the rowspan must remain within the group boundaries of which it is defined.

This example illustrates the order and structure of the table head, foot, and bodies.

<table summary="This table charts the number of cups
of coffee consumed by each senator, the type
of coffee (decaf or regular), and whether
taken with sugar.">
<caption>Cups of coffee consumed by each senator</caption>
<tbody>
<tr> ...A header row...</tr>
<tr> ...First row of data...</tr>
<tr> ...Second row of data...</tr>
...the rest of the table...</tr>
</tbody>
</table>

The content of a frame can specify destination targets for a selection. This module adds the target attribute to the area and link defining elements. This is defined as a separate
module so it can be included in documents that will be included in frames and documents that use the target feature to open a new window.

In order to take advantage of the XHTML DTD Modules, DTD authors need to define the content model for their DTD. XHTML provides a variety of tools to ease this effort. They are defined in a set of
support modules, instantiated by a main Framework module:

Module DTD/xhtml-framework-2.mod not found!

Note that the module above references a content model module. This module is defined on a per-document type basis in addition to the document type driver file. The Modular framework also relies
upon the following component modules:

The modules in this section are elements of the XHTML DTD implementation that, while hidden from casual users, are important to understand when creating derivative markup languages using the
Modularization architecture.

"Information Technology -- Universal Multiple-Octet Coded Character Set (UCS) -- Part 1: Architecture and Basic Multilingual Plane", ISO/IEC 10646-1:2000. This reference refers to a
set of codepoints that may evolve as new characters are assigned to them. Also, this reference assumes that the character sets defined by ISO 10646 and [UNICODE] remain character-by-character equivalent. This reference also includes future publications of other parts of 10646 (i.e., other than Part 1) that define
characters in planes 1-16.